Tower and mast
As previously mentioned, before installing the transmission equipment or hardware of the network, it is first necessary to have a mast or tower, properly grounded and anchored, in place. It is also necessary to have an electrical connection for the exclusive use of the community cellular site. And finally, in order to do long-distance calling, there must Internet. We recommend a 1mbps symetric connection for a standard site.
Once the community has confirmed that these above-mentioned conditions have been met, the installation of the cellular equipment can proceed. We will now describe the steps to be taken in order to install the cellular hardware. For a list and description of the equipment to be installed go to the section Materials.
- The first step is to verify that the tower and mast are properlyinstalled and anchored and that they are safe to use. This means, at a minimum, that the anchor bolts are tight, that the tensor wires are not loose and that the tower is free from oxidation.
- Once it is determined that it is safe to climb the tower, a harness must be worn. In the case of a mast a ladder can be used. Rhizomatica has designed a mast with a hinged base that allows for easy installation of the hardware with the meast on the ground and then, once ready, pivoting the mast up on the hinge and locking it in place with tensor wires and a bolt at the base.
Installation of BTS and antennas
- The next step is to fix the equipment on the tower, using the appropriate mounting hardware (u-bolts, hose clamps, wire, etc). To mount the BTS, use the U-bolts and mounting plate provided with the equipment. The BTS and mounting hardware is designed to be outside in the elements.
- Then mount the power supply unit of the BTS to the tower or mast using appropriately sized hose clamps. Although the power supply unit itself is designed to be outside, the point where it connects to the electrical supply must be protected from humidity in order to avoid a short circuit. The other cable of the power supply unit that connects to the BTS uses a special outdoor-rated plastic connector that is water-tight.
The power supply unit provided with the BTS comes with the above-mentioned outdoor plastic connecotr, but this must be soldered onto the correct cable of the power supply unit in a particular way.
To properly connect the connector it is important to distinguish the polarity of the cables and the terminals of the connector itself. The red cable must be soldered to the positive terminal (+) and the black cable to the negative terminal (-) as indicated in the diagram below. Please note that the diagram's perspective is looking at the internal or back part of the connector where the soldering pins are located:
Once the connector has been soldered to the power supply unit, a standard AC electrical plug can be installed on the other side. Use the green cable to your ground pin and the other two wires can be installed to the phase or positive pins.
- It is recommended to use a plastic or metal cabinet (must be water-tight) in order to house power supplies and protect electrical connections from weather and humidity. These cabinets can be mounted to the tower or mast in different ways, preferably using metal.
- Once the BTS has been mounted to the mast or tower, proceed to mounting the antennas that will connect to the BTS. In the case of directional or panel antennas, they can be mounted directly to the tower or mast.
However, in the case of omnidirectional antennas, it is necessary to separate the transmit antennas from the tower or mast by at least 1 meter. This is done to avoid interference with the waves emitted by the antenna being caused by the structure of the tower or mast. In both cases, the receive antenna should be installed above the BTS and the transmit antenna below the BTS, with a separation of at least 2 meters on the vertical plane.
The receive antennas is mounted using the hardware provided with the antenna, usually a mounting plate and a U-bolt
The metal mounting arm (for separting the omni transmit antenna, if necessary) is attached to the mast or tower with hose clamps. It may also be necessary to run a bolt through the mounting arm and tower so that it doesn't rotate or spin due to wind.
In this photo one can see the distance between the receive antenna (top), the BTS and the metal separation arm where the transmit antenna will be mounted.
The transmit antenna is mounted to the separator arm with the included hardware
- Once the antennas and BTS are securely mounted they must be connected to one another with coaxial cable and N connectors (male). Ensure that the connectors are tight, in this case hand-tight. Do not use pliers or a wrench in order to screw in the coaxial cables. The strength of your hand is sufficient and ensures you won't damage the connectors. Once connected and screwed-in, cover the connector with electrical tape, then a layer of coaxial sealing tape, and then a final layer of electrical tape. Make sure to use electrical tape suitable for exterior use, such as Scotch Super 33 and wrap the connector from bottom (where the cable starts) to top (where the connector ends at the end of the cable). On the tower, the ground is bottom and the sky is top, if that helps to orient. Then do the same with the coaxial sealing tape, ensuring no air bubbles are present and that it is smooth, and then a final layer of electrical tape, starting from the bottom and ending at the top. This ensures water won't get into the connectors or cables.
The following links are videos that show how to wrap the electrical and coaxial tapes:
- With the GSM transmit and receive antennas installed, we can proceed to connec the GPS anenna to the BTS. This antenna generally has a magnet, which makes it easy to stick to any metallic surface. It is recommended to use a couple of zip ties to further secure the antenna to the mast or tower. The SMA connector then is screwed into the corresponding connector on the BTS.
- In cases where the BTS and BSC are not installed at the same site, it is necessary to create a data link between the two, which is most easily done using WiFi antennas. One WiFi antenna is placed on the tower or mast with the BTS and the other at the location of the BSC, ensuring line-of-site between the two WiFi antennas. Mounting hardware and instructions are included with the WiFi antennas.
Once the WiFi antenna is mounted securely on the mast or tower, an ethernet cable is connected to the port on the back of the antenna. This cable is connected to the Power-over-Ethernet (PoE) port on the adapter/power supply and the LAN port connected to the BTS via another ethernet cable. Make sure to close the plastic flap that protects the port on the back of the WiFi antenna.
Ensure you do this with much care and don't force the connectors or connect the BTS to PoE instead of LAN. In order to connect the WiFi antennas to the power supply/adapter, measure the length, cut the cable appropriately, separate out the copper wires inside the cable, and connect the RJ-45 connector.
For the end of the ethernet cable that will connect to the BTS, ensure that the water-tight sleeve is on the ethernet cable before attaching and crimping the RJ-45 connector.
Note: It is extremely important that the ethernet cables are connected to the correct ports on the power supply/adapter. BTS is connected to LAN and the WiFi antenna to PoE. If PoE is connected to the BTS, it can cause damage to the BTS. So NEVER connect BTS to PoE port directly.
- If BTS and BSC are at the same location (same building), it isn't necessary to install WiFi antennas, as BTS and BSC can connect directly via an ethernet cable.
Installing the BSC (physical installation)
- Now we will connect the Base Station Controller (BSC). This computer controls the BTS, and the two can be connected via ethernet cable. The BSC is also connected to the Internet and the Administration computer via ethernet. The following diagram explains the set-up:
- Ethernet cables should be connected on the back of the BSC in the following way:
|LAN 1||LAN 2||LAN 3||LAN 4|
- If a WiFi link has been installed, it's ethernet cable (LAN port on the power supply/adapter) should connect to the LAN 2 port on the back of the BSC. Again it is important the the PoE port only connect to the WiFi antenna and never to the BSC or BTS as this can damage them.
- The community must supply a PC in order to use for the administration of the cellular network. This computer will generally sit next to the BSC as indicated above in the image.
- Once everything is in place, it should be connected to an electricity source via a No-Break/UPS or at minimum a voltage regulator in order to suppress voltage spikes that might damage the equipment.
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